Heating devices have been used in exhaust systems upstream of emission control devices to reduce emissions. For instance, a heater may be positioned upstream of a catalyst to enable adjustment in the temperature of the exhaust stream entering the catalyst. The increased exhaust gas temperature can increase conversion efficiency in the catalyst and decrease emissions. The amount of the heat generated by the heater may be adjusted to reduce emissions over a range of engine operating conditions. However, the heaters have fixed positions and can generate a large amount of back pressure during engine operation. Back pressure decreases engine efficiency and power output and increases engine fuel consumption.
In one approach, an exhaust system in an internal combustion engine is provided to overcome at least some of the drawbacks of previous exhaust systems. The exhaust system includes an exhaust manifold receiving exhaust gas from a cylinder, an emission control device positioned downstream of the exhaust manifold, an electric heating device positioned in an exhaust line upstream of the emission control device and downstream of the exhaust manifold, the electric heating device including a frame at least partially surrounding a heating element, and an adjustment device configured to, during operation of the internal combustion engine, adjust the drag generated by the electric heating device in an exhaust gas flow through the exhaust line. Adjusting the amount of flow resistance generated by the electric heating device enables the back pressure generated by the electric heating device to be reduced during selected time intervals, such as when heating of exhaust gas is not desired. Decreasing back pressure during these conditions can increase engine efficiency and power output and decrease engine fuel consumption.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.